For the safe operation of electromotors, the materials used must not become overheated in the given operating conditions. One must make sure that no overheating occurs when the electromotor is run with maximum dissipation at the ambient temperature. To disregard this can result in the life of the electromotor being shortened or to a complete breakdown of the electromotor.
Therefore, cooling or dissipating the heat from the electromotor, i.e. removing the lost heat, especially from the winding, and from the electromagnetically active iron material, is extremely important.
In the case of electromotors used, for example, to drive ventilators, it is known to direct an air flow through the electromotor, using a difference in pressure between air inlet openings in the electromotor and air outlet openings in order to generate a cooling air flow.
Thus, for example, the European patent application EP 1 050 682 A2 shows a ventilator drive comprising a fixed internal stator with windings and an external rotor that is permanent magnetically excited. On the exterior of the stator base there are control electronics, which are covered by a separate cover. When in operation, a ventilator hub attached to the external rotor in a fixable manner generates a cooling air flow through internal ventilation blades arranged on the inside of the ventilator hub. The cooling air flow enters into the inside of the motor from the side, between the stator base part and the edge of the rotor and exits out into the environment through openings in the edge area of the rotor floor and the space between the outer wall of the stator and the ventilator hub. Thereby, the cooling air flow can only take up heat energy from the stator windings in the inside of the motor housing and dissipate it to the outside. Thus the cooling air flow can only produce an effect to a very limited extent.